1. Field of the Invention
The present invention relates to a fuel cell system and transport equipment including the same, and more specifically, the present invention relates to a fuel cell system which returns unused fuel aqueous solution from a fuel cell to an aqueous solution tank, and also relates to transport equipment such as a motorcycle which utilizes the novel fuel cell system.
2. Description of the Related Art
JP-A 2004-79210 (hereinafter referred to as “Patent Document 1”) discloses a technique for removing byproducts, ionic byproducts or metal ions from a liquid produced in a fuel cell system.
Although the technique disclosed in Patent Document 1 enables collection of hazardous substances occurring in a fuel cell stack, this technique leaves the following problems unaddressed.
Specifically, fuel cells utilized in office equipment such as a personal computer typically operate in a temperature range of from room temperature to 40° C. Therefore, when carbon dioxide is discharged from the aqueous solution tank, not much methanol as the fuel is gasified and discharged simultaneously. However, in a direct methanol fuel cell which operates at a temperature not lower than 50° C., and more specifically at a relatively high temperature of around 65° C., a greater amount of methanol is gasified and discharged from the aqueous solution tank together with carbon dioxide. This is undesirable from an environmental viewpoint.
The problem of discharging methanol into the outside environment cannot be solved by applying the technique in Patent Document 1 to the direct methanol fuel cell system, because Patent Document 1 makes no reference to the problem of how to deal with the methanol gas in the aqueous solution tank.